The invention concerns a process for the determination of the start of an active signal packet, which is also known as a “burst”.
In a case of a wireless LAN-network, and also with other applications, especially regarding mobile radio transmission, digitally modulated signals are emitted in the so-called bursts. That is to say, the signal is only transmitted by bursts. Exclusive of the bursts, there is no transmission. The burst is identical with the term signal section, or signal packet.
In particular, in the case of systems transmitting evaluation data for a Radio LAN System, and also for other mobile radio signals, determination must be made of the start of the active signal packet, that is to say, the chronological burst beginning position. The received signal is next continually received, and it is in the received signal that the start of the active signal packet is to be determined.
Up to this time, it was a conventional practice, that for the determination of the beginning of an active signal packet, correlation procedures without correction for frequency were employed. As to the state of the technology, reference can be made to DE 100 54 517 A1, which deals with an effective synchronization including a reference sequence, namely pn-sequence. Since the said pn-sequence in the case of said employment had a very long periodicity, the proposal was made, to form subinterval groups, and by means of appropriate linear, pair arranged placements and interrupted summations of these subintervals, the troublesome correlation could be shortened. An application in connection with the determination of the beginning of an active signal packet, however, is not described in the cited example.
Disadvantageously, where the prior known correlation procedure was employed, is that the length of the correlation in the presence of a (as a rule) readily available frequency offset between the received signal and the reference signal is limited. Following a phase rotation of 180° between the received signal and the reference signal, the additional correlation-products offer no constructive advantages.
Thus the invention has the purpose of making available a process for the determination of the start of an active signal packet in a digital received signal with the use of a digital reference signal, whereby the correlation between the received signal and the reference signal is so improved, that a correlation of a more lengthy correlation-length can be carried out.